1. Field of the Invention
The present invention relates to an optical pickup, and more particularly to an optical pickup in which a control element as a heating part and a radiator plate are mounted on a base member with the travel thereof being adapted to be guided by a main shaft and a secondary shaft.
2. Description of the Prior Art
There have conventionally been proposed various kinds of optical pickups for making recording onto and/or reproduction from a disk as a recording medium (refer to Japanese Patent Laid-Open Publication Nos. 2000-67457 and 2001-307371 for example).
Japanese Patent Laid-Open Publication No. 2000-67457 includes descriptions of, for example, techniques for: passing guide shafts through a guide hole and a U-shaped guide portion provided, respectively, in two parts on the left and the right of a frame so that the frame can be moved in the radial direction of an optical recording disk; mounting a light source unit with a laser diode, a light detecting element, and a hologram element packed therein by resin molding on the frame; and exposing a grounding wire through a window of the light source unit and bringing a radiator plate into contact with the grounding wire as a measure for improving the radiation performance of the light source unit.
Also, Japanese Patent Laid-Open Publication No. 2001-307371 includes descriptions of, for example, techniques for: protecting a mirror and a prism attached to a resin frame of an optical pickup device using a metal radiator plate attached to the rear surface of the resin frame; and urging a laser diode and a light receiving element toward the resin frame using an elastic endplate portion formed in the radiator plate so that the laser diode and the light receiving element can be positioned and that the heat thereof can be released outward.
Meanwhile, FIG. 4 is a perspective view of a base member 1 of an optical pickup as a comparative example. The base member 1 is a die-cast product and is arranged in such a manner that the optical axis of an optical system to be formed between a laser diode (as a light source not shown in the figure) and the recording surface of a disk runs through approximately the central part thereof. Then, the base member 1 is provided with a sliding bearing 2 adapted to be guided by a metal main shaft 101 that is attached to a traverse chassis (not shown in the figure) on one side of an optical axis, passing point “a”, and with a secondary bearing part 3 supported slidably by a secondary shaft 102 that is attached to the traverse chassis on the other side of the optical axis, passing point “a”. In respect to the sliding bearing 2 and the secondary bearing part 3, the sliding bearing 2 is fitted slidably to the main shaft 101 with almost no backlash, whereby the main shaft 101 with the sliding bearing 2 fitted thereto exerts a substantial guiding effect when the optical pickup travels in the radial direction of a disk. On the other hand, the secondary bearing part 3 comprises a main support piece 31 and an auxiliary support piece 35 positioned, respectively, over and under the secondary shaft 102 in a sandwich manner. Then, the main support piece 31 is disposed slidably over the secondary shaft 102 in an overlapping manner, which can prevent the occurrence of the base member 1 rotating downward around the main shaft 101 due to its own weight, etc., while the auxiliary support piece 35 is disposed slidably under the secondary shaft 102 in an overlapping manner, which can prevent the occurrence of the base member 1 rotating upward around the main shaft 101 for some reasons. Therefore, the secondary bearing part 3 is uplifted from the secondary shaft 102. For this reason, since the guiding effect of the secondary bearing part 3, when the optical pickup travels, is adapted only to assist the guiding effect of the main shaft 101, it is not necessary that the secondary bearing part 3 be fitted with no backlash to the secondary shaft 102. Hence, in the base member 1 shown in FIG. 4, the spacing between the main support piece 31 and the auxiliary support piece 35 is predefined so that a clearance δ (refer to FIG. 3) is ensured between the secondary shaft 102 and the auxiliary support piece 35 when the main support piece 31 is in contact with the upper end of the secondary shaft 102, whereby the ease of assembly is improved and the sliding resistance against the secondary shaft 102 in a sliding operation is reduced to improve the traveling stability of the base member 1. It is noted that the traverse chassis is equipped with a turntable for rotating a disk placed thereon.
In addition, a printed circuit board 4 is mounted on the base member 1. The printed circuit board 4 includes a control element (IC) 41 for controlling the emission of a laser diode (as a light source) mounted thereon. The control element 41 is accompanied by elevated temperatures through its operation, and it is necessary to take a measure for suppressing the elevated operating temperatures to improve the performance. Generally, it is thus often the case that a radiator plate (not shown in FIG. 4) is mounted on the printed circuit board 4 to take a measure for suppressing the elevated operating temperatures in the control element 41 utilizing the radiation effect of the radiator plate.
In the case of ensuring such a clearance δ between the secondary bearing part 3 and the secondary shaft 102 for the purpose of improving the ease of assembly, etc. as in the comparative example described with reference to FIG. 4, when the optical pickup is vibrated due to external vibration, the existence of the clearance δ may impair the positional relationship between the optical pickup and a disk that is placed and rotated on the turntable, resulting in a possibility of exerting a negative impact on the performance in writing and reading with respect to the disk.
In this regard, in order to suppress the vibration of the optical pickup, it has been known that it is effective to position the main support piece 31 of the secondary bearing part 3 in elastic contact with the secondary shaft 102 utilizing a spring force. Taking such a measure allows the integrity (vibration resistance) of the optical pickup with the traverse chassis equipped with the turntable to be improved, reducing the possibility of exerting a negative impact on the performance in writing and reading with respect to a disk.
However, in the optical pickup according to the comparative example described with reference to FIG. 4, incorporating a radiator plate for suppressing the elevated operating temperatures in the control element 41 as well as a spring member adapted to give a spring force to position the main support piece 31 of the secondary bearing part 3 in elastic contact with the secondary shaft 102 leads to an increase in the number of parts. The increase in parts results in a reduction in ease of assembly and thereby decreases mass productivity. In addition, under the effect of weight increase due to the increase in the number of parts, the servo performance (e.g. traveling stability) of the optical pickup may possibly be reduced.
In this regard, the above discussed patent documents describe only measures dealing with radiation performance with no description about vibration resistance. Therefore, even if the techniques described in the patent documents may be used, it is impossible to improve the vibration resistance without causing a reduction in ease of assembly and thereby decreasing mass productivity or degrading the servo performance of the optical pickup.